Electronic devices made with metal Schiff base complexes

ABSTRACT

The present invention relates to new electronic devices including a layer comprising a photoactive material and metal Schiff base complex, wherein the metal Schiff base complex is present as a host for the photoactive material or in a layer between the cathode and the photoactive material containing layer, or both.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electronic devices having a layercomprising a metal Schiff base complex. In particular, the metal Schiffbase complex is in an electron transport or hole-blocking layer, or is ahost for a light-emitting material.

2. Background

In organic photoactive electronic devices, such as light-emitting diodes(“OLED”), that make up OLED displays, the organic active layer issandwiched between two electrical contact layers in an OLED display. Inan OLED the organic photoactive layer emits light through thelight-transmitting electrical contact layer upon application of avoltage across the electrical contact layers.

It is well known to use organic electroluminescent compounds as theactive component in light-emitting diodes. Simple organic molecules,conjugated polymers, and organometallic complexes have been used.

Devices which use photoactive materials, frequently include one or morecharge transport layers, which are positioned between the photoactive(e.g., light-emitting) layer and one of the contact layers. A holetransport layer may be positioned between the photoactive layer and thehole-injecting contact layer, also called the anode. An electrontransport layer may be positioned between the photoactive layer and theelectron-injecting contact layer, also called the cathode.

There is a continuing need for charge transport materials.

SUMMARY OF THE INVENTION

There is provided a new organic electronic device comprising a layercomprising a photoactive material and a metal Schiff base complex,wherein the metal Schiff base complex is present as a host for thephotoactive material or included within another layer between thecathode and the photoactive material conataining layer or both layers.

In one embodiment, the metal Schiff base complex has Formula I,M(SB)_(a)L¹ _(b)   Formula (I)wherein:

-   -   M is a metal in a +3 oxidation state;    -   SB is a Schiff base ligand;    -   L¹ is a ligand having the formula Ar—O, where Ar is selected        from an aromatic group and a heteroaromatic group;    -   a is 1, 2, or 3;    -   b is 0, 1,or 2;        with the proviso that the metal Schiff base complex is        electrically uncharged.

In one embodiment, the Schiff base ligand is selected from Structure I,II, III, and IV, below:

wherein:

-   -   R¹, R², R³ are the same or different and are independently        selected from hydrogen, alkyl, heteroalkyl, aryl, and        heteroaryl, or adjacent R groups can join together to form 5- or        6-membered rings; and    -   Z is selected from alkylene, heteroalkylene, arylene, and        heteroarylene;        wherein R¹, R², and R³ are as defined above;        wherein    -   R¹, R², R³, and Z are as defined above;        wherein    -   R¹, R², and R³ are as defined above;    -   R⁴ is selected from hydrogen, alkyl, heteroalkyl, aryl, and        heteroaryl.

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims.

DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not limitation in theaccompanying figures.

FIG. 1: An illustrative example of one new organic electronic device.

FIG. 2: A graph of luminance quenching vs. concentration of a metalSchiff base complex, BAlQ.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A new organic electronic device comprises a layer comprising aphotoactive material a metal Schiff base complex, wherein the metalSchiff base complex is present as a host for the photoactive material orwhere the Schiff base complex is included in another layer between thecathode of the electronic device and the photoactive material containinglayer or both layers. In one embodiment, the layer including the Schiffbase complex is in the layer immediately adjacent to the either thelayer comprising the photoactive material or the cathode. In oneembodiment, the Schiff base complex is included in a layer that is notimmediately adjacent to either the photoactive materials or the cathode.In one embodiment, a Schiff base complex is present as a host for thephotoactive material and at least one second adjacent layer as mentionabove.

As used herein, the term “photoactive” is intended to mean a materialthat emits light when activated by an applied voltage (such as in alight-emitting diode or light-emitting electrochemical cell), a materialthat responds to radiant energy and generates a signal with or withoutan applied bias voltage (such as in a photodetector), or a material thatconverts radiation into an electrical signal (such as in a photovoltaiccell).

The term “complex”, when used as a noun, is intended to mean a compoundhaving at least one metallic ion and at least one ligand. The term“ligand” is intended to mean a molecule, ion, or atom that is attachedto the coordination sphere of a metallic ion. The term “Schiff base”refers to a compound formed by a condensation reaction between a primaryamine (aliphatic or aromatic) and an aldehyde or ketone. The term “metalSchiff base complex” refers to a metal complex having one or more Schiffbase ligands. The term “host” refers to a material which is present witha photoactive material. The host facilitates light emission by thephotoactive material. In one embodiment, the host is present in anamount greater than 50% by weight, based on the total weight of thephotoactive layer.

In one embodiment, the metal Schiff base complex has Formula I,M(SB)_(a)L¹ _(b)   Formula Iwherein:

-   -   M is a metal in a +3 oxidation state;    -   SB is a Schiff base ligand;    -   L¹ is a ligand having the formula Ar—O, where Ar is selected        from an aromatic group and a heteroaromatic group;    -   a is 1, 2, or 3;    -   b is 0, 1, or 2;        with the proviso that the metal Schiff base complex is        electrically uncharged.

In one embodiment of Formula I, the metal is selected from Al, Zn, andGa. In one embodiment, the metal is Al.

In one embodiment of Formula I, the Schiff base ligand is selected fromStructure I, II, III, and IV, below:

wherein:

-   -   R¹, R², R³ are the same or different and are independently        selected from hydrogen, alkyl, heteroalkyl, aryl, and        heteroaryl, or adjacent R groups can join together to form 5- or        6-membered rings; and    -   Z is selected from alkylene, heteroalkylene, arylene, and        heteroarylene;        wherein R¹, R², and R³ are as defined above;        wherein    -   R¹, R², R³, and Z are as defined above;        wherein    -   R¹, R², and R³ are as defined above;    -   R⁴ is selected from hydrogen, alkyl, heteroalkyl, aryl, and        heteroaryl.        Although not shown, each of the oxygen atoms in the above        structures carries a negative charge. The Schiff base ligands        are derived from electrically uncharged Schiff base compounds in        which each oxygen is bonded to a hydrogen atom.

In one embodiment, the metal Schiff base complex has Formula I(a)M(SB)L¹   Formula I(a)and SB has Structure I. The metal is pentacoordinate when nocoordinating atom is present in Z, and hexacoordinate when acoordinating atom is present.

In one embodiment of Structure I, both R¹ are the same and both R² arethe same. In one embodiment, in each instance adjacent R¹ and R² jointogether to form a 6-membered aromatic ring. In one embodiment, thearomatic ring is further substituted with a group selected from an alkylgroup, a heteroalkyl group, an alkenyl group, a heteroalkenyl group, analkynyl group, a heteroalkynyl group, an aryl group, including fusedrings, a heteroaryl group, an alkoxy group, an aryloxy group, andhalide.

In one embodiment of Structure I, R³ is selected from hydrogen, phenyl,and methyl.

Examples of suitable groups for Z include, but are not limited to,alkylene having from 1-20 carbon atoms, phenylene, arylene having from 2to 4 fused rings, bi-arylene, and aza-alkylene having from 2-20 carbonatoms. Such groups can be unsubstituted or substituted.

In one embodiment of Structure I, Z is selected from alkylene havingfrom 1-6 carbon atoms; 1,2-cyclohexylene; 1,2-phenylene;4-methoxy-1,2-phenylene; 4,5-dimethyl-1,2-phenylene;o-binaphthalene-diyl; 3-aza-1,5-pentylene; 1,2-o-tolyl-1,2-ethylene;1,2-dicyano-1,2-ethylene; and 2-p-t-butylbenzyl-1,3-propylene.

In one embodiment of Structure I, Z is selected from ethylene,1,2-cyclohexylene, and —CH₂CH₂NHCH₂CH₂—. The 1,2-cyclohexylene can be ineither a cis or trans configuration.

In one embodiment of Formula I(a), Ar is selected from phenyl, biphenyl,and naphthyl. In one embodiment, the aromatic ring is furthersubstituted with a group selected from an alkyl or aryl group.

In one embodiment, the metal Schiff base complex having Formula I(a) isselected from Complexes 1 through 6 below:

In one embodiment, the metal Schiff base complex has Formula I(b),M(SB)   Formula I(b)and SB has Structure II. The metal is pentacoordinate.

In one embodiment of Structure II, all R¹ are the same and all R² arethe same. In one embodiment, in each instance adjacent R¹ and R² jointogether to form a 6-membered aromatic ring. In one embodiment SB hasStructure II(a):

where there are from 0 to 4 R⁵ groups, and each

-   -   R⁵ is the same or different at each occurrence and is        independently selected from an alkyl group, a heteroalkyl group,        an alkenyl group, a heteroalkenyl group, an alkynyl group, a        heteroalkynyl group, an aryl group, a heteroaryl group, an        alkoxy group, an aryloxy group, an amino group, and halide, or        adjacent R⁵ groups can be joined together to form 5- or        6-membered rings; and    -   c is 0, 1, 2, 3, or 4.        In one embodiment, R⁵ is selected from t-butyl, methoxy, chloro,        diethylamino, and fused phenyl, and c is 1 or 2.

In one embodiment of Structure II, R³ is selected from hydrogen, phenyl,and methyl.

In one embodiment, the metal Schiff base complex has Formula I(a) and SBhas Structure III. When there is no coordinating atom in Z, the metal istetracoordinate. When a coordinating atom is present in Z, the metal ispentacoordinate.

In one embodiment of Structure III, R¹ and R² join together to form a6-membered aromatic ring. In one embodiment, the aromatic ring isfurther substituted with a group selected from an alkyl group, aheteroalkyl group, an alkenyl group, a heteroalkenyl group, an alkynylgroup, a heteroalkynyl group, an aryl group, including fused rings, aheteroaryl group, an alkoxy group, an aryloxy group, and halide. In oneembodiment, the aromatic ring is selected from fluorophenyl andalkylphenyl, where the alkyl has from 1 to 6 carbon atoms.

Examples of suitable groups for Z include, but are not limited to,alkylene having from 1-20 carbon atoms, phenylene, arylene having from 2to 4 fused rings, bi-arylene, aza-alkylene having from 2-20 carbonatoms, and substituted versions thereof.

In one embodiment of Structure III, Z is selected from alkylene havingfrom 1-6 carbon atoms; 1,2-cyclohexylene; 1,2-phenylene;4-methoxy-1,2-phenylene; 4,5-dimethyl-1,2-phenylene;o-binaphthalene-diyl; 3-aza-1,5-pentylene; 1,2-o-tolyl-1,2-ethylene;1,2-dicyano-1,2-ethylene; and 2-p-t-butylbenzyl-1,3-propylene.

In one embodiment of Structure III, Z is selected from ethylene,1,2-cyclohexylene, and —CH₂CH₂NHCH₂CH₂—. The 1,2-cyclohexylene can be ineither a cis or trans configuration.

In one embodiment of Formula I(a), Ar in ligand L¹ is selected fromphenyl, biphenyl, and naphthyl. In one embodiment, the aromatic ring isfurther substituted with a group selected from an alkyl or aryl group.

In one embodiment, the metal Schiff base complex has Formula I(c) orI(d),M(SB)₂L¹   Formula I(c)M(SB)₃ Formula I(d)and SB has Structure IV. The metal is pentacoordinate in Formula I(c)and hexacoordinate in Formula I(d).

In one embodiment of Structure IV, R¹ and R² join together to form a6-membered aromatic ring. In one embodiment, the aromatic ring isfurther substituted with a group selected from an alkyl group, aheteroalkyl group, an alkenyl group, a heteroalkenyl group, an alkynylgroup, a heteroalkynyl group, an aryl group, including fused rings, aheteroaryl group, an alkoxy group, an aryloxy group, and halide. In oneembodiment, the aromatic ring is selected from dichlorophenyl andalkylphenyl, where the alkyl has from 1 to 6 carbon atoms.

In one embodiment of Structure IV, R⁴ is selected from alkyl having 1-20carbon atoms and phenyl. In one embodiment, R⁴ is further substitutedwith at least one group selected from halide and alkoxy groups.

In one embodiment of Formula I(c), Ar in ligand L¹ is selected fromphenyl, biphenyl, and naphthyl. In one embodiment, the aromatic ring isfurther substituted with a group selected from an alkyl group and anaryl group.

In general, the Schiff base compounds can be prepared by the reaction ofan aldehyde or a ketone with a primary amine, as illustratedschematically below:

Such reactions are well known. Schiff base compounds having Structure Ican be prepared by the reaction of a primary diamine with anhydroxy-aldehyde or ketone, in a 1:2 molar ratio. Schiff base compoundshaving Structure II can be prepared by the reaction of2,2′,2″-tris(aminoethyl)amine, having three primary amine groups, withan hydroxy-aldehyde or ketone, in a 1:3 molar ratio. Schiff basecompounds having Structure III can be prepared by the reaction of aprimary aminoalcohol with an hydroxy-aldehyde or ketone, in a 1:1 molarratio. Schiff base compounds having Structure IV can be prepared by thereaction of a primary amine with an hydroxy-aldehyde or ketone, in a 1:1molar ratio.

The metal Schiff base complex can generally be prepared by combining theSchiff base with a trivalent metal compound, in an appropriate solvent.Metal compounds such as metal alkoxides or organometallic compounds suchas triethylaluminum can be used. Metal salts such as acetates, nitrates,or chlorides can also be used.

Organic electronic devices that may benefit from having one or morelayers comprising a metal Schiff base complex include, but are notlimited to, (1) devices that convert electrical energy into radiation(e.g., a light-emitting diode, light emitting diode display, or diodelaser), (2) devices that detect signals through electronics processes(e.g., photodetectors., photoconductive cells, photoresistors,photoswitches, phototransistors, phototubes, IR detectors), (3) devicesthat convert radiation into electrical energy, (e.g., a photovoltaicdevice or solar cell), and (4) devices that include one or moreelectronic components that include one or more organic semi-conductorlayers (e.g., a transistor or diode).

One illustration of an organic electronic device structure is shown inFIG. 1. The device 100 has an anode layer 110 and a cathode layer 160,and a photoactive layer 130 between them. Adjacent to the anode is alayer 120 comprising hole transport material. Adjacent to the cathode isa layer 140 comprising an electron transport material. As an option,devices frequently use another electron transport layer or electroninjection layer 150, next to the cathode.

The metal Schiff base complex can function as a host for the photoactivematerial in layer 130. When present as a host, the metal Schiff basecomplex should be physically compatible with the photoactive material,so that the materials do not separate into separate phases. The host isgenerally present in an amount greater than 50% by weight, based on thetotal weight of the photoactive layer. In one embodiment, the host ispresent in an amount greater than 60% by weight. In one embodiment, thehost is present in an amount greater than 75% by weight. The metalSchiff base complex and photoactive material can be applied by a vaporco-deposition process, when applicable, by a solution deposition processfrom a common solution, or by a thermal transfer process.

The metal Schiff base complex can function as an electron transportmaterial, hole blocking material, anti-quenching material, orcombinations thereof, in layer 140. The metal Schiff base complex can beapplied by a vapor deposition process, when applicable, by a solutiondeposition process, or by a thermal transfer process.

Depending upon the application of the device 100, the photoactive layer130 can be a light-emitting layer that is activated by an appliedvoltage (such as in a light-emitting diode or light-emittingelectrochemical cell), a layer of material that responds to radiantenergy and generates a signal with or without an applied bias voltage(such as in a photodetector). Examples of photodetectors includephotoconductive cells, photoresistors, photoswitches, phototransistors,and phototubes, and photovoltaic cells, as these terms are describe inMarkus, John, Electronics and Nucleonics Dictionary, 470 and 476(McGraw-Hill, Inc. 1966).

The other layers in the device can be made of any materials which areknown to be useful in such layers. The anode 110, is an electrode thatis particularly efficient for injecting positive charge carriers. It canbe made of, for example materials containing a metal, mixed metal,alloy, metal oxide or mixed-metal oxide, or it can be a conductingpolymer, and mixtures thereof. Suitable metals include the Group 11metals, the metals in Groups 4, 5, and 6, and the Group 8-10 transitionmetals. If the anode is to be light-transmitting, mixed-metal oxides ofGroups 12, 13 and 14 metals, such as indium-tin-oxide, are generallyused. The anode 110 may also comprise an organic material such aspolyaniline as described in “Flexible light-emitting diodes made fromsoluble conducting polymer,” Nature vol. 357, pp 477-479 (11 Jun. 1992).At least one of the anode and cathode should be at least partiallytransparent to allow the generated light to be observed.

Examples of hole transport materials for layer 120 have been summarizedfor example, in Kirk-Othmer Encyclopedia of Chemical Technology, FourthEdition, Vol. 18, p. 837-860, 1996, by Y. Wang. Both hole transportingmolecules and polymers can be used. Commonly used hole transportingmolecules include, but are not limited to:N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC),N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)-[1,1′-(3,3′-dimethyl)biphenyl]-4,4′-diamine(ETPD), tetrakis-(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA),a-phenyl4-N,N-diphenylaminostyrene (TPS), p-(diethylamino)benzaldehydediphenylhydrazone (DEH), triphenylamine (TPA),bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP),1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl]pyrazoline(PPR or DEASP), 1,2-trans-bis(9H-carbazol-9-yl)cyclobutane (DCZB),N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB),and porphyrinic compounds, such as copper phthalocyanine. Commonly usedhole transporting polymers include, but are not limited to,polyvinylcarbazole, (phenylmethyl)polysilane, and polyaniline. It isalso possible to obtain hole transporting polymers by doping holetransporting molecules such as those mentioned above into polymers suchas polystyrene and polycarbonate.

Any organic electroluminescent (“EL”) material can be used as thephotoactive material in layer 130. Such materials include, but are notlimited to, fluorescent dyes, fluorescent and phosphorescent metalcomplexes, conjugated polymers, and mixtures thereof. Examples offluorescent dyes include, but are not limited to, pyrene, perylene,rubrene, derivatives thereof, and mixtures thereof. Examples of metalcomplexes include, but are not limited to, metal chelated oxinoidcompounds, such as tris(8-hydroxyquinolato)aluminum (Alq3);cyclometalated iridium and platinum electroluminescent compounds.Examples of conjugated polymers include, but are not limited topoly(phenylenevinylenes), polyfluorenes, poly(spirobifluorenes),polythiophenes, poly(p-phenylenes), copolymers thereof, and mixturesthereof.

In one embodiment of the new device, the photoactive material is anorganometallic complex. In one embodiment, the photoactive material is acyclometalated complex of iridium or platinum. Complexes of Iridium withphenylpyridine, phenylquinoline, or phenylpyrimidine ligands have beendisclosed as electroluminescent compounds in Petrov et al., PublishedPCT Application WO 02/02714. Other organometallic complexes have beendescribed in, for example, published applications U.S. 2001/0019782, EP1191612, WO 02/15645, and EP 1191614. Electroluminescent devices with anactive layer of polyvinyl carbazole (PVK) doped with metallic complexesof iridium have been described by Burrows and Thompson in published PCTapplications WO 00/70655 and WO 01/41512. Electroluminescent emissivelayers comprising a charge carrying host material and a phosphorescentplatinum complex have been described by Thompson et al., in U.S. Pat.No. 6,303,238, Bradley et al., in Synth. Met. (2001), 116 (1-3),379-383, and Campbell et al., in Phys. Rev. B, Vol. 65 085210. Examplesof a few suitable iridium complexes are given in FIG. 6, as FormulaeIV(a) through IV(e). Analogous tetradentate platinum complexes can alsobe used. These electroluminescent complexes can be used alone, or dopedinto charge-carrying hosts, as noted above.

Examples of electron transport materials which can be used in optionallayer 150 include metal chelated oxinoid compounds, such astris(8-hydroxyquinolato)aluminum (Alq₃); and azole compounds such as2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) and3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ);phenanthrolines such as 4,7-diphenyl-1,10-phenanthroline (DPA) and2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA); and mixturesthereof.

The cathode 160, is an electrode that is particularly efficient forinjecting electrons or negative charge carriers. The cathode can be anymetal or nonmetal having a lower work function than the anode. Materialsfor the cathode can be selected from alkali metals of Group 1 (e.g., Li,Cs), the Group 2 (alkaline earth) metals, the Group 12 metals, includingthe rare earth elements and lanthanides, and the actinides. Materialssuch as aluminum, indium, calcium, barium, samarium and magnesium, aswell as combinations, can be used. Li-containing organometalliccompounds, LiF, and Li₂O can also be deposited between the organic layerand the cathode layer to lower the operating voltage.

It is known to have other layers in organic electronic devices. Forexample, there can be a layer (not shown) between the anode 110 and holetransport layer 120 to facilitate positive charge transport and/orband-gap matching of the layers, or to function as a protective layer.Layers that are known in the art can be used. In addition, any of theabove-described layers can be made of two or more layers. Alternatively,some or all of anode layer 110, the hole transport layer 120, theelectron transport layers 140 and 150, and cathode layer 160, may besurface treated to increase charge carrier transport efficiency. Thechoice of materials for each of the component layers is preferablydetermined by balancing the goals of providing a device with high deviceefficiency with device operational lifetime.

It is understood that each functional layer may be made up of more thanone layer.

The device can be prepared by a variety of techniques, includingsequentially depositing the individual layers on a suitable substrate.Substrates such as glass metal, ceramic and polymeric films andcombinations thereof can be used. Conventional vapor depositiontechniques can be used, such as thermal evaporation, chemical vapordeposition, and the like. Alternatively, the organic layers can beapplied by liquid deposition using suitable solvents or other liquidmedia to create a solution, dispersion, emulsion or suspension. Typicalliquid deposition techniques include, but are not limited to, continuousdeposition techniques such as spin coating, gravure coating, curtaincoating, dip coating, slot-die coating, casting, spray-coating, barcoating, roll coating, doctor blade coating and continuous nozzlecoating; and discontinuous deposition techniques such as ink jetprinting, gravure printing, and screen printing. Other techniques forappling organic layers include thermal transfer.

In one embodiment, the different layers have the following range ofthicknesses: anode 110, 500-5000 Å, in one embodiment 1000-2000 Å; holetransport layer 120, 50-2000 Å, in one embodiment 200-1000 Å;photoactive layer 130, 10-2000 Å, in one embodiment 100-1000 Å; layers140 and 150, 50-2000 Å, in one embodiment 100-1000 Å; cathode 160,200-1000 Å, in one embodiment 300-5000 Å. The location of theelectron-hole recombination zone in the device, and thus the emissionspectrum of the device, can be affected by the relative thickness ofeach layer. Thus the thickness of the electron-transport layer should bechosen so that the electron-hole recombination zone is in thelight-emitting layer. The desired ratio of layer thicknesses will dependon the exact nature of the materials used.

As used herein, the term “alkyl” is intended to mean a group derivedfrom an aliphatic hydrocarbon having one point of attachment. The term“alkenyl” is intended to mean a group derived from a hydrocarbon havingone or more carbon-carbon double bonds and having one point ofattachment. The term “alkynyl” is intended to mean a group derived froma hydrocarbon having one or more carbon-carbon triple bonds and havingone point of attachment. The term “aryl” is intended to mean a groupderived from an aromatic hydrocarbon having one point of attachment. Theterm “alkoxy” refers to an alkyl group attached to an oxygen atom, andfurther attached to another molecule by the oxygen. The term “aryloxy”refers to an aryl group attached to an oxygen atom, and further attachedto another molecule by the oxygen.

The term “group” is intended to mean a part of a compound, such as asubstituent in an organic compound or a ligand in a complex.

The term “compound” is intended to mean an electrically unchargedsubstance made up of molecules that further consist of atoms, whereinthe atoms cannot be separated by physical means.

The term “layer” is used interchangeably with the term “film” and refersto a coating covering a desired area. The area can be as large as anentire device or a specific functional area such as the actual visualdisplay, or as small as a single sub-pixel. Films can be formed by anyconventional deposition technique, including vapor deposition and liquiddeposition.

The term “organometallic compound” is intended to mean a compound havinga metal-carbon bond. The organometallic compound may include metal atomsfrom Groups 3 through 15 of the Periodic Table and mixtures thereof.

The term “tetracoordinate” is intended to mean that four groups orpoints of attachment are coordinated to a central metal. The term“pentacoordinate” is intended to mean that five groups or points ofattachment are coordinated to a central metal. The term “hexacoordinate”is intended to mean that six groups or points of attachment arecoordinated to a central metal.

The term “charge transport” is intended to refer to a material that canreceive a charge from an electrode and facilitate its movement throughthe thickness of the material with relatively high efficiency and smallloss of charge. Electron transport materials are capable of receiving anegative charge from a cathode and transporting it. The term “holeblocking” refers to a material which prevents, retards, or diminishesthe transfer of a hole through the thickness of the material. The term“anti-quenching” is intended to refer to a material which prevents,retards, or diminishes both the transfer of energy and the transfer ofan electron to or from the excited state of the photoactive layer to anadjacent layer.

The prefix “hetero” indicates that one or more carbon atoms has beenreplaced with a different atom.

Unless otherwise indicated, all groups can be unsubstituted orsubstituted, and, when applicable, all groups can be linear, branched orcyclic. The phrase “adjacent to,” when used to refer to layers in adevice, does not necessarily mean that one layer is immediately next toanother layer. On the other hand, the phrase “adjacent R groups” is usedto refer to R groups that are next to each other in a chemical formula(i.e., R groups that are on atoms joined by a bond).

The IUPAC number system is used throughout, where the groups from thePeriodic Table are numbered from left to right as 1-18 (CRC Handbook ofChemistry and Physics, 81^(st) Edition, 2000).

As used herein, the phrase “X is selected from the group consisting ofA, B, and C” is intended to mean that X is A, or X is B, or X is C. Thephrase “X is selected from 1 through n” is intended to mean that X is 1,or X is 2 . . . or X is n.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of the “a” or “an” are employed to describe elements andcomponents of the invention. This is done merely for convenience and togive a general sense of the invention. This description should be readto include one or at least one and the singular also includes the pluralunless it is obvious that it is meant otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Unless otherwise defined, allletter symbols in the figures represent atoms with that atomicabbreviation. Although methods and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresent invention, suitable methods and materials are described below.All publications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Incase of conflict, the present specification, including definitions, willcontrol. In addition, the materials, methods, and examples areillustrative only and not intended to be limiting.

EXAMPLES

The following examples illustrate certain features and advantages of thepresent invention. They are intended to be illustrative of theinvention, but not limiting. All percentages are by weight, unlessotherwise indicated.

Examples 1-6

Examples 1-6 illustrate the preparation of Schiff base complexes havingFormula I(a)M(SB)L¹   Formula I(a)where the Schiff base ligand has Structure I.

Example 1

This example illustrates the preparation of Complex 1.

Schiff base compound SB-1 was first prepared:

Schiff base compound SB-1 was prepared by taking 5.15 gdiethylenetriamine into 250 mL methanol under nitrogen and adding 13.6 g2-hydroxyacetophenone also in 250 mL methanol. After refluxing undernitrogen with vigorous stirring, the solution turned yellow and solidformed in the flask. TLC confirmed that the reaction was complete, andthe solid was recovered by filtration and extensive washing withmethanol. Yield 93%.

2.04 g aluminum isopropoxide and 3.4 g SB-1 were taken into 50 mL warmethanol in a nitrogen-filled glove box and stirred with mild warminguntil completely dissolved. To this was added 1.7 g 2-phenylphenol withcontinued heating and stirring. While stirring, the solution rapidlysolidified and the pale yellow solid was collected by filtration andwashed with ethanol. After suction drying the solid was poorly solublein methylene chloride. Analysis by nmr in d6-DMSO confirmed thecomposition as Complex 1. Yield 76%.

Example 2

This example illustrates the preparation of Complex 2.

2.04 g aluminum isopropoxide and 3.4 g SB-1 were taken into 50 mL warmethanol in a nitrogen-filled glove box and stirred with mild warminguntil completely dissolved. To this was added 1.7 g 4-phenylphenol withcontinued heating and stirring. While stirring, the solution rapidlysolidified and the pale yellow solid was collected by filtration andwashed with ethanol. After suction drying the solid was poorly solublein methylene chloride. Analysis by nmr in d6-DMSO confirmed thecomposition as Complex 2. Yield 85%.

Example 3

This example illustrates the preparation of Complex 3.

2.04 g aluminum isopropoxide and 3.4 g SB-1 were taken into 50 mL warmethanol in a nitrogen-filled glove box and stirred with mild warminguntil completely dissolved. To this was added 2.5 g 2,6-diphenylphenolwith continued heating and stirring. While stirring the solution rapidlysolidified and the pale yellow solid was collected by filtration andwashed with ethanol. After suction drying the solid was poorly solublein methylene chloride. Analysis by nmr in d6-DMSO confirmed thecomposition as Complex 3. Yield 69%.

Example 4

This example illustrates the preparation of Complex 4.

Schiff base compound SB-2 was first prepared:

SB-2 was prepared by dissolving 9.38 g 3,5-di-t-butylbenzaldehyde into aminimum volume of hot methanol in a flask and adding 2.3 gcis-diaminocyclohexane predissolved in 50 mL methanol. This mixture wasrefluxed under nitrogen for 4 hours, checking progress with TLC. Thecooled solution was filtered to collect yellow crystals of the desiredproduct, which were washed extensively with cold methanol. Yield 91%.

2.04 g aluminum isopropoxide and 3.0 g SB-2 were dissolved into a mixedsolvent of methylene chloride and ethanol (1:1 by volume, total volumeof 100 mL) in a nitrogen-filled glove box. 1.7 g of 4-phenylphenol solidwas added and stirred vigorously while heating in the glove box. Thismixture was refluxed for 30 minutes, then cooled. The methylene chloridewas removed by evaporation. The resultant pale yellow solid wascollected by filtration, washed well with ethanol, and suctioned dry.Yield 77%.

Example 5

This example illustrates the preparation of Schiff base complex, Complex5.

Schiff base compound SB-3 was first prepared:

SB-3 was prepared by taking 13.6 g 2-hydroxyacetophenone into 50 mLmethanol and adding 1 mL acetic acid. With vigorous stirring, 3.0 gethylene diamine also dissolved in 50 mL methanol was added. After 4 hrsreflux, the solution was cooled and the solid crystals recovered byfiltration and extensive washing with cold methanol. Yield 87%.

In a nitrogen-filled glove box, 6 mL triethylaluminum in hexane (1M) wasadded to a solution of 1.8 g SB-3 in 50 mL toluene with vigorousstirring. Care was taken to avoid foaming. This was refluxed briefly todissolve, after which a cloudy precipitate formed. Then 0.34 g4-phenylphenol was added to the cooled solution slowly to avoid foaming.This was heated and stirred for over 30 minutes at close to boiling.After cooling, a crystalline white precipitate was collected.

Example 6

This example illustrates the preparation of Schiff base complex, Complex6.

Schiff base compound SB-4 was first prepared:

Compound SB-4 was prepared by taking 13.6 g 2-hydroxyacetophenone into50 mL methanol and adding 1 mL acetic acid. With vigorous stirring, 5.7g trans-1,2-cyclohexyldiamine also dissolved in 50 mL methanol wasadded. After 4 hrs reflux, the solution was cooled and the solidcrystals recovered by filtration and extensive washing with coldmethanol. Yield 93%.

In a nitrogen-filled glove box, 2 mL triethylaluminum in hexane (1M) wasadded to a solution of 0.72 g SB-4 in 10 mL toluene with vigorousstirring. To this was added 0.34 g 4-phenylphenol. This was heated andstirred for >30 minutes at close to boiling. After cooling, the paleyellow/white solid precipitate was collected. The solid was washed wellwith toluene and dried in the glove box.

Examples 7-30

Examples 7-30 illustrate the preparation of Schiff base complexes havingFormula I(b),M(SB)   Formula I(b)and SB has Structure II(a)

Schiff Base Compound SB-5

In this compound R³ is H, and R⁵ is 5,6-fused phenyl.

4.87 g tris-(2-aminoethyl)amine was dissolved into 100 mL dry methanoland then mixed with 17.22 g 2-hydroxy-1-naphthaldehyde also dissolved in100 mL dry methanol. The mixture was stirred under nitrogen at refluxfor 4 hours and then allowed to cool to room temperature, at which pointa yellow precipitate had formed. The solid was collected by filtrationand washed well with methanol and dried in vacuum.

Schiff Base Compound SB-6

In this compound R³ is H, and R⁵ is 3,5-di-t-butyl.

2.92 g of tris-(2-aminoethyl)amine was dissolved into 50 mL dry methanoland then mixed with 14.06 g 3,5-di-t-butyl-2-hydroxybenzaldehyde alsodissolved in 50 mL dry methanol. The mixture was stirred under nitrogenat reflux for 4 hours and then allowed to cool to room temperature atwhich point a yellow precipitate had formed. The solid was collected byfiltration and washed well with methanol and dried in vacuum.

Schiff Base Compound SB-7

In this compound, R³ is methyl, and R⁵ is H.

2.92 g of tris-(2-aminoethyl)amine was dissolved into 50 mL dry methanoland then mixed with 8.16 g 2′-hydroxyacetophenone also dissolved in 50mL dry methanol. The mixture was stirred under nitrogen at reflux for 4hours and then allowed to cool to room temperature at which point ayellow ppt had formed. The solid was collected by filtration and washedwell with methanol and dried in vacuum.

Schiff Base Compound SB-8

In this compound, R³ is H, and R⁵ is 3-methoxy.

Schiff Base Compound SB-9

In this compound, R³ is H, and R⁵ is H.

Schiff Base Compound SB-10

In this compound, R³ is H, and R⁵ is 3,5-dichloro.

Schiff Base Compound SB-11

In this compound, R³ is H, and R⁵ is 4-diethylamino.

Aluminum Complexes:

These were prepared in a nitrogen-filled glove box by mixing a solutionof the Schiff base compound in toluene with a solution oftriethylaluminum in hexane, in an approximately 3:1 molar ratio. Themixture evolved ethane gas. It was stirred for 1 hour, during which timea solid formed. This solid was collected by filtration, washed well withhexanes and dried in vacuo.

Other Metal Complexes:

These were prepared by dissolving the Schiff base compound in methanolor a methanol/methylene chloride mixture, and then adding a metal saltdissolved in methanol, in an approximately 3:1 molar ratio. The saltsused were acetates (Y, Sm, Eu, Gd, Tb, Ln, Tm), nitrates (Ga, In), orchlorides (Sc). The mixture was warmed and stirred overnight. The solidwas collected by filtration or evaporation.

All the Schiff base complexes were recrystallized from DMF/methanol(SB-5), toluene/hexane (SB-6), or methylene chloride/hexane (SB-7, SB-8,SB-9, SB-10, SB-11).

The metal Schiff base complexes are summarized in Table 1. TABLE 1 MetalSchiff Base Complexes Having Formula I(b) Example Metal Schiff Base  7Al SB-5  8 Sc SB-5  9 Y SB-5 10 Al SB-6 11 Sm SB-6 12 Eu SB-6 13 Gd SB-614 Tb SB-6 15 Sc SB-6 16 Y SB-6 17 Ga SB-6 18 In SB-6 19 La SB-6 20 TmSB-6 21 Al SB-7 22 Sc SB-7 23 Eu SB-7 24 Tb SB-7 25 Y SB-7 26 Sm SB-7 27Y SB-8 28 Y SB-9 29 Y SB-10 30 Y SB-11

Schiff bases having Structures III and IV were prepared in a similarmanner as those described above. The appropriate monoamine compound wasselected and reacted in a 1:1 molar stoichiometry with the selectedaldehyde or ketone.

Example 31-35

These examples illustrate the use of the metal Schiff base complexes inan OLED device.

General Procedure

OLED devices were fabricated by the thermal evaporation technique. Thebase vacuum for all of the thin film deposition was in the range of 10⁻⁶torr. The deposition chamber was capable of depositing eight differentfilms without the need to break the vacuum. Patterned indium tin oxidecoated glass substrates from Thin Film Devices, Inc were used. TheseITO's are based on Corning 1737 glass coated with 1400 Å ITO coating,with sheet resistance of 30 ohms/square and 80% light transmission. Thepatterned ITO substrates were then cleaned ultrasonically in aqueousdetergent solution. The substrates were then rinsed with distilledwater, followed by isopropanol, and then degreased in toluene vapor.

The cleaned, patterned ITO substrate was then loaded into the vacuumchamber and the chamber was pumped down to 10⁻⁶ torr. The substrate wasthen further cleaned using an oxygen plasma for about 5 minutes. Aftercleaning, multiple layers of thin films were then deposited sequentiallyonto the substrate by thermal evaporation. Patterned metal electrodes(Al or LiF/Al) were deposited through a mask. The thickness of the filmswas measured during deposition using a quartz crystal monitor. Thecompleted OLED device was then taken out of the vacuum chamber andcharacterized immediately without encapsulation.

The OLED samples were characterized by measuring their (1)current-voltage (I-V) curves, (2) electroluminescence radiance versusvoltage, and (3) electroluminescence spectra versus voltage. The I-Vcurves were measured with a Keithley Source-Measurement Unit Model 237.The electroluminescence radiance (in units of cd/m²) vs. voltage wasmeasured with a Minolta LS-110 luminescence meter, while the voltage wasscanned using the Keithley SMU. The electroluminescence spectrum wasobtained by collecting light using an optical fiber, through anelectronic shutter, dispersed through a spectrograph, and then measuredwith a diode array detector. All three measurements were performed atthe same time and controlled by a computer. The efficiency of the deviceat a certain voltage is determined by dividing the electroluminescenceradiance of the LED by the current density needed to run the device. Theunit is a cd/A.

The devices had the structure shown in FIG. 1. Layer 140 was either ametal Schiff base complex, or, in the comparative example, BAlQ. Thematerials had the structures shown below. MPMP:

G1, a green emitter:

BAlQ:

AlQ:

Device materials and layer thicknesses are summarized in Table 2. Thedevice properties are given in Table 3. TABLE 2 Device ArchitectureExample Layer 120 Layer 130 Layer 140 Layer 150 Layer 160 Comp. A MPMPG1 BAIQ AIQ LiF - 10 301 404 101 302 Al - 505 31 MPMP G1 Complex 4 AIQLiF - 10 304 402 102 303 Al - 505 32 MPMP G1 Complex 1 AIQ LiF - 10 303402 103 303 Al - 505 33 MPMP G1 Complex 2 AIQ LiF - 10 304 404 104 303Al - 300 34 MPMP G1 Complex 6 AIQ LiF - 10 302 402 101 301 Al - 504 35MPMP G1 Complex 5 AIQ LiF - 10 304 402 102 303 Al - 505All thicknesses are in Angstroms.

TABLE 3 Device Properties Peak Radiance Peak Efficiency Example cd/m²cd/A Comparative A 9300 at 16 V 26 31 6000 at 21 V 21 32 8000 at 19 V 1733 6200 at 19 V 27 34 6000 at 19 V 20 35 8000 at 24 V 19

Example 36

This example illustrates the low level of luminance quenching of Complex2.

In one embodiment, the metal Schiff base complexes disclosed herein havelow photo-luminescence quenching efficiency towards emitters. If a hostor an electron transport material shows high photoluminescence quenchingefficiency, the device will show low electroluminescent efficiency,especially if the recombination zone is in contact with the material. Tomeasure the quenching efficiency, the following photoluminescentquenching experiments were performed.

The luminescence quenching of an excited molecule can be described asA*+Q=X   (1)where A* represents the luminescent excited state of the emitter, Qrepresents the quencher (in this case the charge transport or hostmolecule under study), and X represents the product of the quenchingreaction. The degree of quenching can be evaluated quantitatively bydetermining the rate constant of the luminescence quenching, k_(q), inthe above equation. The value of k_(q) can be obtained, for example, bythe well-known Stern-Volmer equation:(I _(q) /I ₀)−1=k _(q) T ₀ [Q]  (2)where I_(q) represents the luminescence intensity of the emitter in thepresence of the quencher, I₀ represents the intensity in the absence ofthe quencher, T₀ is the luminescent excited state lifetime in theabsence of the quencher, and [Q] is the concentration of the quencher.By plotting (I_(q)/I₀)−1 vs [Q], the slope of the straight line givesk_(q) T₀, which is known as the Stern-Volmer quenching constant. If T₀is known, then one obtains the luminescence quenching rate constant,k_(q). Even if the exact value of T₀ were unknown, the quenching rateconstants of different charge transport and/or anti-quenching materialsmay be accurately compared because T₀ is a constant.

FIG. 2 compares the Stern-Volmer quenching plots of Complex 2 and BAlQ,towards the G1 green emitter. The slope of the line gives theStern-Volmer quenching constant. Complex 2 has a Stern-Volmer quenchingconstant of 497, compared to BAlQ with a Stern-Volmer quenching constantof 4142. This indicates complex 2 has a lower luminance quenching effecttowards G1, and therefore intrinsically a better electron transport orhost material.

1. An organic electronic device comprising a cathode, a layer comprisinga photoactive material positioned there between and a metal Schiff basecomplex, wherein the metal Schiff base complex is present as a host forthe photoactive material or in a layer between a cathode and thephotoactive material containing layer or in both layers.
 2. An organicelectronic device according to claim 1, wherein the metal Schiff basecomplex has Formula (I)M(SB)_(a)L¹ _(b)   Formula (I) wherein: M is a metal in a +3 oxidationstate; SB is a Schiff base ligand; L¹ is a ligand having the formulaAr—O, where Ar is selected from an aromatic group and a heteroaromaticgroup; a is 1, 2, or 3; b is 0, 1, or 2; with the proviso that the metalSchiff base complex is electrically uncharged.
 3. An organic electronicdevice according to claim 2, wherein M is selected from Al, Zn, and Ga.4. An organic electronic device according to claim 2, wherein the Schiffbase ligand is selected from Structure I, II, III, and IV, below:

wherein: R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings; andZ is selected from alkylene, heteroalkylene, arylene, and heteroarylene;

wherein: R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings;

wherein: R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings; andZ is selected from alkylene, heteroalkylene, arylene, and heteroarylene;

wherein: R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings; andR⁴ is selected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl.5. An organic electronic device according to claim 1, wherein the metalSchiff base complex has Formula I(a)M(SB)L¹   Formula I(a) wherein M is a metal in a +3 oxidation state; L¹is a ligand having the formula Ar—O, where Ar is selected from anaromatic group and a heteroaromatic group; SB is a Schiff base ligandhaving Structure I:

wherein: R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings; andZ is selected from alkylene, heteroalkylene, arylene, and heteroarylene.6. A device according to claim 5, wherein in each instance adjacent R¹and R² join together to form a 6-membered aromatic ring.
 7. A deviceaccording to claim 6, wherein the aromatic ring is further substitutedwith a group selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl,alkynyl, heteroalkynyl, aryl, heteroaryl, alkoxy, aryloxy, and halide.8. A device according to claim 5, wherein R³ is selected from hydrogen,phenyl, and methyl.
 9. A device according to claim 5, wherein Z isselected from alkylene having from 1-20 carbon atoms, phenylene, arylenehaving from 2 to 4 fused rings, bi-arylene, and aza-alkylene having from2-20 carbon atoms.
 10. A device according to claim 5, wherein Z isselected from alkylene having from 1-6 carbon atoms; 1,2-cyclohexylene;1,2-phenylene; 4-methoxy-1,2-phenylene; 4,5-dimethyl-1,2-phenylene;o-binaphthalene-diyl; 3-aza-1,5-pentylene; 1,2-o-tolyl-1,2-ethylene;1,2-dicyano-1,2-ethylene; and 2-p-t-butylbenzyl-1,3-propylene.
 11. Adevice according to claim 5, wherein Z is selected from ethylene,1,2-cyclohexylene, and —CH₂CH₂NHCH₂CH₂—.
 12. A device according to claim5, wherein Ar is selected from phenyl, biphenyl, and naphthyl.
 13. Adevice according to claim 1, wherein the metal Schiff base complex isselected from Complexes 1 through 6:


14. A device according to claim 1, wherein the metal Schiff base complexhas Formula I(b)M(SB)   Formula I(b) wherein: M is a metal in a +3 oxidation state; SBis a Schiff base ligand having Structure II:

wherein R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings. 15.A device according to claim 14, wherein in each instance adjacent R¹ andR² join together to form a 6-membered aromatic ring.
 16. A deviceaccording to claim 15, wherein the aromatic ring is further substitutedwith a group selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl,alkynyl, heteroalkynyl, aryl, heteroaryl, alkoxy, aryloxy, and halide.17. A device according to claim 15, wherein the aromatic ring is3,5-di(t-butyl)phenyl or naphthyl.
 18. A device according to claim 15,wherein R³ is selected from hydrogen, phenyl, and methyl.
 19. A deviceaccording to claim 1, wherein the metal Schiff base complex has FormulaI(a)M(SB)L¹   Formula I(a) wherein M is a metal in a +3 oxidation state; L¹is a ligand having the formula Ar—O, where Ar is selected from anaromatic group and a heteroaromatic group; SB is a Schiff base ligandhaving Structure III:

wherein: R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings; andZ is selected from alkylene, heteroalkylene, arylene, and heteroarylene.20. A device according to claim 19, wherein in each instance adjacent R¹and R² join together to form a 6-membered aromatic ring.
 21. A deviceaccording to claim 20, wherein the aromatic ring is further substitutedwith a group selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl,alkynyl, heteroalkynyl, aryl, heteroaryl, alkoxy, aryloxy, and halide.22. A device according to claim 19, wherein R³ is selected fromhydrogen, phenyl, and methyl.
 23. A device according to claim 19,wherein Z is selected from alkylene having from 1-20 carbon atoms,phenylene, arylene having from 2 to 4 fused rings, bi-arylene, andaza-alkylene having from 2-20 carbon atoms.
 24. A device according toclaim 19, wherein Z is selected from alkylene having from 1-6 carbonatoms; 1,2-cyclohexylene; 1,2-phenylene; 4-methoxy-1,2-phenylene;4,5-dimethyl-1,2-phenylene; o-binaphthalene-diyl; 3-aza-1,5-pentylene;1,2-o-tolyl-1,2-ethylene; 1,2-dicyano-1,2-ethylene; and2-p-t-butylbenzyl-1,3-propylene.
 25. A device according to claim 19,wherein Z is selected from ethylene, 1,2-cyclohexylene, and—CH₂CH₂NHCH₂CH₂—.
 26. A device according to claim 19, wherein Ar isselected from phenyl, biphenyl, and naphthyl.
 27. A device according toclaim 1, wherein the metal Schiff base complex has Formula I(c) or I(d),M(SB)₂L¹   Formula I(c)M(SB)₃   Formula I(d) wherein: M is a metal in a +3 oxidation state; SBis a Schiff base ligand having Structure IV:

wherein R¹, R², R³ are the same or different and are independentlyselected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl, oradjacent R groups can join together to form 5- or 6-membered rings; andR⁴ is selected from hydrogen, alkyl, heteroalkyl, aryl, and heteroaryl.28. A device according to claim 14, wherein in each instance adjacent R¹and R² join together to form a 6-membered aromatic ring.
 29. A deviceaccording to claim 28, wherein the aromatic ring is further substitutedwith a group selected from alkyl, heteroalkyl, alkenyl, heteroalkenyl,alkynyl, heteroalkynyl, aryl, heteroaryl, alkoxy, aryloxy, and halide.30. A device according to claim 28, wherein the aromatic ring isdichlorophenyl or alkylphenyl.
 31. A device according to claim 27,wherein R⁴ is selected from alkyl having 1-20 carbon atoms and phenyl.32. A device according to claim 31, wherein R⁴ is further substitutedwith a halide group or alkoxy group.